This study is designed to assess the safety and efficacy of adrenal medullary rafts and fetal mesencephalic grafts in patients with severe Parkinson's disease. The patients selected will have Stage IV disease, but still show some response to oral dopamine replacement therapy. The patient will undergo extensive testing preoperatively including gait, posture, reaction time, speech, and neuropsychiatric assessment. Cavities will be created in the right caudate nucleus via a transcallosal approach, and a ventricular reservoir placed. Two weeks later one adrenal gland will be removed, and placed into the preformed cavity (or fetal mesencephalic tissue will be placed in the cavity and no adrenalectomy performed). The preoperative testing will be repeated at regular intervals after implantation. CSF biochemistry and 6-fluorodopa PET studies will also be part of the testing carried out. One patient has received an adrenal medullary autograft. He has shown mild improvement with reduction of the severity of his on/off fluctuations and improved mobility during his "off " time. In addition, he has had a lessening of the dyskinesias which limit his tolerance for oral therapy. The CSF studies have revealed an elevation of enkephalin in the first few months compared to preoperatively, but no long-lasting elevation of enkephalin or elevation of catecholamines. No patients have received fetal mesencephalic grafts due to a ban on such work by the Department of Health and Human Services.